A FRENCH government minister said yesterday that he was preparing a plan for liberating Serbian detention camps in Bosnia. Bernard Kouchner, the Health and Humanitarian Action Minister, speaking after Roland Dumas, the Foreign Minister, had said the camps should be freed by force if need be, said he would 'very quickly - tonight or tomorrow - propose a plan'. Howver, he said that current UN resolutions did not authorise the use of force.

The US administration has said it is aware of 175 camps in Bosnia and Serbia, three-quarters of them in the hands of Serbs.

The issue was, at best, confused as differing interpretations were offered of Mr Dumas' words in a radio interview on Sunday. Condemning the Serbian camps, an instrument of 'ethnic cleansing', he said 'nothing is now in the way of convoys accompanied by protection forces going to the camps and freeing them. And I myself asked Mr Kouchner today to provide for, if need be for ourselves and by ourselves, the organisation of convoys of this kind . . . '

This cumbersome formulation was largely taken to mean that

Mr Dumas envisaged unilateral military action by France, something that President Francois Mitterrand ruled out in his New Year message.

Pierre Joxe, the Defence Minister, meeting journalists yesterday, pointed out that only Mr Mitterrand, as chief of the army, could decide on how France's armed forces could be used. 'He decides when, where and by what means we will fulfil whatever mission for the UN,' Mr Joxe said.

Mr Dumas, he said, envisaged action only under the aegis of the UN. Mr Joxe said there was no difference of opinion between himself and the Foreign Minister.

Daniel Bernard, Mr Dumas' spokesman, reinforced the impression that France was at least trying to lead the way: 'Somebody must take the initiative on something. We propose to do something because we consider the current situation unacceptable. We propose doing something practical and concrete right away.'

Le Monde newspaper said in a commentary that France risked being 'justly reproached for acting alone' by its European partners. It suggested that Mr Dumas' stance might have been motivated by the murder of Hakija Turajlic, the Bosnian Deputy Prime Minister, on Friday by a Serbian militiaman while he was under escort of French UN soldiers on the outskirts of Sarajevo, and by the proximity of elections in March.

Radovan Karadzic, the Bosnian Serbs' leader, who is in Geneva for the Bosnian peace talks, issued a statement attacking Mr Dumas. 'I am astonished that this intervention has come in the middle of the peace talks. It can only be seen as an election stunt,' he said.

Malcom Rifkind, the Secretary of State for Defence, said last night that there were contingency plans to reinforce British UN forces in Bosnia, and that the carrier Ark Royal, in Portsmouth, might be sent to the Adriatic to support UN ground forces or to help enforce an air exclusion zone with its Harrier interceptors.

The Cabinet's Overseas Policy and Defence Committee meets today. Mr Rifkind said 'We are giving careful thought to what support needs to be given. We're taking two things into account. The possibility that the UN might make a decision on enforcing the no-fly zone and the incidents last week (Friday and Sunday) when our forces were attacked . . .

'You can assume that whatever may be required for the proper protection of our troops will be made available. That may change as the threat changes.'

Mr Rifkind said the Ark Royal 'could be useful as a way of providing a base'. He also said it would be of value in a withdrawal - its Sea King helicopters could be used to evacuate troops or casualties - 'but we are not considering that at the present time'.

Asked whether the 'proper protection' of British troops meant artillery, Mr Rifkind said he did not rule it out. On Friday the Tomislavgrad base came under artillery attack and on Sunday British troops shot back with 30mm Rarden cannon after being mortared by the Serbs.